E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Frenchmen, properly Parisians. So called from their ancient heraldic device, which was three frogs or three toads. Quen disent les grenouilles?What will the frogs (people of Paris) say?was in 1791 a common court phrase at Versailles. There was a point in the pleasantry when Paris was a quagmire, called Lutetia (mud-land) because, like frogs or toads, they lived in mud, but now it is quite an anomaly. (See CRAPAUD.)
Frogs. The Lycian shepherds were changed into frogs for mocking Latona. (Ovid: Metamorphoses, vi. 4.)
As when those hinds that were transformed to frogs
Railed at Latonas twin-born progeny.
Milton: Sonnet, vii.
It may be all fun to you, but it is death to the frogs. The allusion is to the fable of a boy stoning frogs for his amusement.